Battery knowledge · Units and electrical basics
Impedance
The frequency-dependent generalisation of resistance, with a magnitude and a phase. A cell’s impedance separates ohmic, charge-transfer and diffusion contributions that a single DC resistance lumps together.
- Abbreviation
- Z
- Unit
- Ω
Example
Read an impedance semicircle
High-frequency intercept: 10 mΩ. Arc width: 30 mΩ. Low-frequency intercept: 40 mΩ.
No diffusion tail or inductive loop. The plotted aspect ratio may distort the semicircle.
Explore the graph
A series resistance plus one parallel RC branch gives a single semicircle.
High-frequency intercept: 10 mΩ. Arc width: 30 mΩ. Low-frequency intercept: 40 mΩ.
Z = R₀ + R₁ / (1 + jωR₁C)
Illustrative model. No diffusion tail or inductive loop. The plotted aspect ratio may distort the semicircle.
Use in Lemonergy
Lemonergy Studio blocks
State-space impedance worked example
Continuous current-to-voltage linear dynamics with direct feedthrough. User supplies identified matrices.
Blocks to use
- State-space impedance
Solves a user-supplied continuous linear state model from current inputs to voltage outputs. Dense matrices support multiple input/output channels and direct feedthrough. Matrices are displayed as rows in configuration.
Inputs & settings
- Use the parameter values in the block reference.
- Bundled example verified on the production release of 28 October 2026.
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Review the block inputs, units and model limits.
- Open the Studio example and run its bundled model.
- Compare the output channels with the numerical checks; change one input and run again.
Example. Use the defaults below with Current inputs = [2] A. At 0 s, Voltage outputs is [0.02] V. Additional checks are listed below.
Observe. Inspect the outputs and numerical checks on the block reference page.
At most 16 states and eight inputs or outputs. The model author must identify stable, physically meaningful matrices and consistent units. No automatic impedance fitting is performed. The example verifies numerical behavior for synthetic parameters. Cell characterization and validation for an intended use are separate tasks.
Open Studio example →References & further reading
Further reading on this topic
These sources provide broader context; they are not presented as citations for every statement in this entry.
- The International System of Units (SI), 9th edition
Bureau International des Poids et Mesures · 2026
Topic background · Definitions of SI units and coherent derived units; 2026 revision.